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Proceedings Paper

Subattomole detection in the condensed phase by nonlinear laser spectroscopy based on degenerate four-wave mixing
Author(s): William M. Tong
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Paper Abstract

Laser spectroscopy based on degenerate four-wave mixing (D4WM) has been demonstrated to offer excellent spectral resolution since the signal is inherently Doppler free. When using a low-pressure demountable discharge cell, Lorentzian (pressure) broadening is also minimized. In addition to excellent spectral resolution, this nonlinear laser method also offers excellent detection sensitivity for gas-phase samples. The authors demonstrate that this nonlinear laser method can be used also as a highly sensitive analytical method to detect trace amounts of analyte in the condensed phase using continuously flowing liquid cells at room temperature. Both pulsed lasers and relatively low-power continuous-wave lasers can be used to generate the signal. Since the signal is detected against virtually a dark background and the signal beam is a time-reversed replica of the probe laser beam, optical signal can be most efficiently collected. Condensed phase D4WM detection sensitivity is comparable or better than those of laser-based fluorescence methods and yet D4WM is applicable for detection of both fluorescing and non- fluorescing molecules. Therefore, room-temperature degenerate four-wave mixing has many applications in analytical chemistry, especially when interfaced to continuously flowing chemical separation methods including liquid chromatography and capillary electrophoresis.

Paper Details

Date Published: 1 July 1991
PDF: 5 pages
Proc. SPIE 1435, Optical Methods for Ultrasensitive Detection and Analysis: Techniques and Applications, (1 July 1991); doi: 10.1117/12.44235
Show Author Affiliations
William M. Tong, San Diego State Univ. (United States)

Published in SPIE Proceedings Vol. 1435:
Optical Methods for Ultrasensitive Detection and Analysis: Techniques and Applications
Bryan L. Fearey, Editor(s)

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